IEEE P802.11
Wireless LANs
Date: 2016-08-29
Author(s):
Name / Affiliation / Address / Phone / email
SK Yong / Apple Inc. / 6 Infinite Loop, Cupetino, CA, USA / skyong [at] apple.com
5001 / "The Service Combination field is present only if the Number of Available Services field is set to 0." In other words: it is only valid in a "query" type of operation. However, the Service Hash element is defined only for Beacon and ProbeResponse frames, which are used for a "response" type operation. / Remove Service Combination field and associated text from the Service Hash element, or allow the Service Hash element in a ProbeRequest frame, so the Service Combination field can be used in a "query" operation.
5009 / the format of the Servicece Hash element is bizzare. Since the service hash is only included in Probe Response/Beacon, why the AP wants to indicate if the AP offered different combinations of different services (with "and" and "or" permutations). This added unnecessary complexity with no benifit / remove flags field and service combination fields and assocaited text
Instruction to Editor
Update the section 9.4.2.217 as follows:
9.4.2.217 Service Hash element
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3 The Service Hash element contains one or more service hashes and a logical function to interpret the combi-
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5 nation of service hashes. The format of the Service Hash element is shown in Figure 9-586m (Service Hash
6 element format).
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12 Octets: 1 1 1 2 variable variable
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Figure 9-586m—Service Hash element format
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20 The Element ID, Length and Element ID Extension fields are defined in 9.4.2.1 (General).
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22 The Flags field is defined in Figure 9-586n (Flags field format).
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31 Bits: 6 6 4
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Figure 9-586n—Flags field format
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39 The Number of Included Services field indicates the number of service hashes that are included in the ele-
40 ment. This field is set to a nonzero value.
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42 A value of r for the Number of Available Services field indicates availability of at most r services among
43 those specified by the service hashes included in the element. Any value of the Number of Available Ser-
45 vices field that is equal to or greater than the value of the Number of Included Services field indicates avail-
46 ability of all the services included in the element. The field is set to 0 only when providing a combination of
47 services included in the element that cannot be described by an “any r-of-n” format.
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49 The Service Hashes field contains one or more 6-octet service hash values. See 11.25a.4 (Service hash pro-
51 cedures) for procedures for generating a service hash used in the Service Hash element.
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53 The Service Combination field is present only if the Number of Available Services field is set to 0. The Ser-
54 vice Combination field carries a service combination bitmap that is 2n bits in length, where n is the number
55 of service hashes in the element, and is organized into é2n/8ù octets such that bit number b (0 ≤ b 2n) in the
57 bitmap corresponds to bit number (b mod 8) in octet number ëb/8û, where the low order bit of each octet is
58 bit number 0, and the high order bit is bit number 7. The service combination bitmap is the sum-of-products
59 representation of a boolean function of n boolean variables x1,....,xn where xi (i = 1,...,n) indicates search for
60 the service corresponding to the i-th service hash included in the element. Specifically, bit b (0 ≤ b 2n) in
61 the bitmap corresponds to minterm mb in a sum-of-products representation.
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64 NOTE—To illustrate the Service Combination field format consider a STA that provides service S1 or service S2 or both
65 services S3 and S4, where services S1, S2, S3 and S4 appear in the Service Hash element in that order. The provided ser-
Aug 2015 doc.: IEEE 802.11-16/1120r0
1 vice combination can be represented by the boolean function x1 + x2 + x3.x4, or the sum of minterms m1, m2, m3, m5,
2 m6, m7, m9, m10, m11, m12, m13, m14, and m15 using the sum-of-product representation. The resulting bitmap is
1111111011101110 binary, and the value of the Service Combination field is 0xFEEE.
CID / Comment / Proposed Change5004 / The below definition is flaw for the purpose of 11aq. "service information registry: A logical entity that contains caches of information about services that may be available via the BSS for the STA to connect to after it associates with the AP."
The cached service information (at least some portion of them) shall be available prior to association rather than only available after the STA associated to the AP. . Similarly in subclause 4.5.9.1.3, this needs to be fix. / make changes to reflect the cahced info is available for preassocaition discovery
Submission page 4 SK Yong, Apple Inc.